Such gas generators conventionally comprise a reaction or combustion chamber in which the gas is generated and which is surrounded by a ring-shaped filter chamber. Flow openings are provided in the wall which separates the reaction or combustion chamber from the filter chamber. Further flow openings are provided in the filter chamber wall for permitting the generated and filtered gas to enter into the article or device, such as a so-called "air bag" in an impact protection system.
German Patent Publication (DE-AS) 2,915,202 discloses a gas generator of the above described type. It is desirable for such inflating devices, especially when an air bag for a safety system is to be inflated, that the inflating satisfies a certain efficiency. Stated differently, a safety air bag must be inflated to a certain degree or rather to a certain internal pressure within a defined inflating time. Additionally, the inflating time and the inflating pressure shall be as much as possible independent of the gas generator temperature at the time of ignition of the gas generating fuel. The gas generator temperature may be within the range of about -40.degree. C. to about +85.degree. C. However, conventional gas generators are noticeably dependent in their efficiency from the temperature to which they are exposed at the time of the ignition. As a result, the air safety bag is inflated, for example at a temperature of -40.degree. C., much slower and to a lesser inflation pressure than when the same generator is exposed to a higher temperature at the time of ignition.
On the other hand, the inflating characteristic or efficiency of the gas generator must also be satisfactory when the generator is exposed to a high temperature, for example, of +85.degree. C. In conventional gas generators the inflating time at high temperatures is respectively shorter and the inflating pressure of the safety bag is very high. As a result, the safety bag must be constructed to withstand the higher pressures when the inflating takes place with high gas generator temperatures. This makes the air bags relatively more expensive and such air bags become heavier. Still another undesirable characteristic of such air bags with a high inflated pressure resides in the fact that the intended cushioning effect may be substantially reduced.
Further, when the gas generating fuel is combusted, hot particles travel from the combustion chamber into the filter chamber where these particles are supposed to be filtered out of the inflating gas. The discharge of the hot particles from the reaction or combustion chamber into the filter chamber also depends on the temperature of the gas generator. In other words, at a high temperature of about +85.degree. C. a relatively large proportion of hot particles exits from the reaction chamber. As a result, the filter and the filter chamber must be constructed to meet the operating conditions at such high temperature. Such construction again makes the filter chamber and the filter itself more expensive.